code: def test_unsupported_conversion(self):
      feature_names = self.scikit_data.feature_names
      output_name = "target"
      xgb_model = xgboost.XGBRegressor(objective="reg:gamma")
      xgb_model.fit(self.scikit_data.data, self.scikit_data.target)
      with self.assertRaises(ValueError):
          spec = xgb_converter.convert(
              xgb_model, feature_names, "target"
          )
  
      xgb_model = xgboost.XGBRegressor(objective="reg:tweedie")
      xgb_model.fit(self.scikit_data.data, self.scikit_data.target)
      with self.assertRaises(ValueError):
          spec = xgb_converter.convert(
              xgb_model, feature_names, "target"
          )
  
file_path: coremltools/coremltools/test/xgboost_tests/test_boosted_trees_regression.py
imports: import json
  import tempfile
  import unittest
  from coremltools._deps import _HAS_SKLEARN, _HAS_XGBOOST
  from coremltools.models.utils import _macos_version
label_desc: Use image node_id 4 for calling the BoostedTreeRegressorXGboostTest obj's underlying member method code with example usage: obj.test_unsupported_conversion() without return types